In our lab, we have been developing apertureless THz near-field microscopes (THz-NFMs) based on an atomic force microscope (AFM), both theories and measurement techniques (KR Patent 10-1466807 and US/Japan/Germany Patents pending). At present, our THz-NFM is the only one in the world that can do broadband (0.3-2 THz) THz pulse near-field imaging with nanometer spatial resolution

Self-Consistent Near-Field Scattering Theory

We demonstrated quantitative analysis and measurements of near-fields interactions in a terahertz pulse near-field microscope. We developed a self-consistent line dipole image method for the quantitative analysis of the near-field interaction in THz scattering-type scanning optical microscopes. The measurements of approach curves and relative contrasts on gold and silicon substrates were in excellent agreement with calculations.

Quantitative Coherent Scattering Spectra of THz Near-Field Microscope

THz Broadband Subsurface Nanoimaging

Combined with terahertz (THz) time-domain spectroscopy, THz near-field microscopy based on an atomic force microscope is a technique that, while challenging to implement, is invaluable for probing low-energy light-matter interactions of solid-state and biomolecular nanostructures, which are usually embedded in background media. Here, for the first time, we experimentally demonstrate a broadband THz pulse near-field microscope that provides subsurface nanoimaging of a metallic grating embedded in a dielectric film. The THz near-field microscope can obtain broadband nanoimaging of the subsurface grating with a nearly frequency-independent lateral resolution of 90 nm, corresponding to λ/3300, at 1 THz, while the AFM only provides a flat surface topography.